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<title>Concept ObjectTransform</title>
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<a name="ObjectTransform"></a><div class="titlepage"></div>
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<h2><span class="refentrytitle">Concept ObjectTransform</span></h2>
<p>ObjectTransform</p>
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<div class="refsect1">
<a name="id-1.3.34.5.62.3"></a><h2>Description</h2>
<p>
      An ObjectTransform is a function type or a function
      pointer type where the return type Obj is a
      an object type and the arguments are
      Transforms. is_callable&lt; Obj &gt;::value
      must be false. The ObjectTransform, when applied,
      has the effect of constructing an object of type
      Obj' (see below), passing as construction parameters
      the result(s) of applying transform(s) Tn.
    </p>
<p>
      The type Obj may be a template specialization representing
      a compile-time lambda expression. For instance, if Obj is
      std::pair&lt; proto::_value, int &gt;, the result type of the
      ObjectTransform is computed by replacing the type proto::_value
      with the result of applying the proto::_value transform. For
      given types Obj, Expr, State and Data, we can say that the
      type Obj' represents the type Obj after all nested transforms
      have been replaced with the results of applying the transforms
      with Expr, State and Data as transform arguments.
    </p>
<p>
      If the type Obj is not a template specialization representing
      a compile-time lambda expression, then the result type Obj' is
      the same as Obj.
    </p>
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<div class="refsect1">
<a name="id-1.3.34.5.62.4"></a><h2>Notation</h2>
<div class="variablelist"><dl class="variablelist">
<dt><span class="term">Obj</span></dt>
<dd>A type playing the role of object-type in the <a class="link" href="ObjectTransform.html" title="Concept ObjectTransform">ObjectTransform</a> concept.</dd>
<dt><span class="term">Tn</span></dt>
<dd>A type playing the role of transform-type in the <a class="link" href="ObjectTransform.html" title="Concept ObjectTransform">ObjectTransform</a> concept.</dd>
<dt><span class="term">Expr</span></dt>
<dd>A type playing the role of expression-type in the <a class="link" href="ObjectTransform.html" title="Concept ObjectTransform">ObjectTransform</a> concept.</dd>
<dt><span class="term">State</span></dt>
<dd>A type playing the role of state-type in the <a class="link" href="ObjectTransform.html" title="Concept ObjectTransform">ObjectTransform</a> concept.</dd>
<dt><span class="term">Data</span></dt>
<dd>A type playing the role of data-type in the <a class="link" href="ObjectTransform.html" title="Concept ObjectTransform">ObjectTransform</a> concept.</dd>
<dt><span class="term"><code class="varname">expr</code></span></dt>
<dd>Object of type Expr</dd>
<dt><span class="term"><code class="varname">state</code></span></dt>
<dd>Object of type State</dd>
<dt><span class="term"><code class="varname">data</code></span></dt>
<dd>Object of type Data</dd>
</dl></div>
</div>
<div class="refsect1">
<a name="id-1.3.34.5.62.5"></a><h2>Valid expressions</h2>
<div class="informaltable"><table class="table">
<colgroup>
<col>
<col>
<col>
<col>
</colgroup>
<thead><tr>
<th>Name</th>
<th>Expression</th>
<th>Type</th>
<th>Semantics</th>
</tr></thead>
<tbody><tr>
<td><p>Apply Transform</p></td>
<td><p>when&lt; _, Obj(Tn...)&gt;()(expr, state, data)</p></td>
<td><p><span class="type">Obj'</span></p></td>
<td><p>Applies the transform.</p></td>
</tr></tbody>
</table></div>
</div>
<div class="refsect1">
<a name="id-1.3.34.5.62.6"></a><h2>Models</h2>
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><span class="simplelist"><span class="type">std::pair&lt; boost::proto::_value, int &gt;(boost::proto::_value, int())</span></span></li></ul></div>
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<td align="right"><div class="copyright-footer">Copyright © 2008 Eric Niebler<p>
        Distributed under the Boost Software License, Version 1.0. (See accompanying
        file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
      </p>
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